Snow hydrology part 2 Flashcards
What can be added to the energy equation for delta Q? What other sources of energy are there outside of Q*, latent heat, and sensible heat?
Qr- energy of the rain
Qg- energy from the ground
If the incoming short wave was 500 W/m^2 and the albedo was 0.9, what would K* be ?
Means 90% is reflected, so 50 W/m^2 would be absorbed.
Does shortwave radiation initiate melt?
No, as albedo doesn’t dip during warming period and reflects much of the shortwave radiation coming in. Something else has to initiate snow melt which then decreases albedo and then allows shortwave radiation to contribute to melt.
Once snow melt begins, is short wave radiation evenly dispersed on the melting snow pack? Why not?
No, as slope and aspect will affect it and vegetation will affect it. More vegetation- less K , if facing north slope- less K
What does longwave radiation depend on?
according to stefan-boltzman law the surface temp of the snow, the longwave radiation is usually negative as l down is larger than l up.
If longwave radiation is negative how does it contribute to warming of the snowpack?
It reradiates heat through clouds and atmosphere
How does vegetation play a role in net longwave radiation?
Trees are good longwave emitters because they are dark and absorb solar radiation and re emit it, this causes the hollow sin snow levels around trees
So if shortwave radiation is very small positive due to albedo and longwave radiation is fairly negative as Lup is much higher than Ldown, in what conditions does melting start in terms of radiaition?
When we are at a Q* of 0 and we have cloudy wet atmospheric conditions which can reradiate heat and when atmosphere is warmer than the surface
How can chinooks contribute to warming of snowpack or cooling?
through a sensible heat flux, the chinook is warm air this causes a strong sensible heat flux which causes a warm atmosphere which leads to melting of snow
Also through a latent heat flux, if the humidity is low in the atmosphere and turbid winds come in the snow will get sublimated, lose energy, and then the snow just evaporates instead of melting.
Can also warm through latent heat flux when warm air mass hits cold snow pack, causing condensation and warm water hits snowpack releasing energy and driving snow melt.
What is conductive flux?
Is negligible, where during snow melt ground heat flux causes loss of heat from snowpack as it’s colder and has less energy
Does rain heat flux contribute to melt?
Not by much, rain can freeze, releasing energy and warming snowpack but on a already warm snowpack it won’t do much, so it can heat it up but not melt it.
So what drives Q* to be greater than 0 and initiate snow warming process?
Change in long wave radiation makes it become less albedo heavy as it warms the snowpack, and then incoming solar radiation accelerates the melt. Also natural impurities.
What snow phase is between the warming phase and runoff?
the snow ripening phase, water saturates and fills all the pore spaces before the run off actually happens.
What is the output phase?
Is after the snowpack is ripened and further energy input produces runoff
What can be designed to measure all components of energy balance? What can this tell us?
towers and models, tells us net energy available for snow melt.
